The long search for effective screening strategies to identify ovarian cancer in average-risk women before symptoms occur has proved disappointing.

Now a new understanding of the complexity of the disease further dims hopes for effective early screening in the near future, Duke University researchers say.

“Screening alone with the tests we have now is not going to get us where we want to be,” researcher Laura Havrilesky, MD, of the Duke Cancer Institute, tells WebMD. “We have to look at other ways to reduce deaths from ovarian cancer.”

Ovarian Cancer: Two Diseases

Nearly 22,000 women in the U.S. will be diagnosed with ovarian cancer this year and 14,000 will die of the disease, according to the American Cancer Society (ACS).

Five-year survival when the cancer is found before it has spread beyond the ovaries is more than 90%, but less than 20% of ovarian cancers are detected in the early stage before it has spread outside the ovary.

Ovarian cancer has long been thought of as a single disease, but researchers have recently learned that it has different subtypes, including a relatively slow-growing form and a more aggressive form that takes about half the time to progress to advanced stages.

Using this knowledge, Havrilesky and colleagues developed a computer-based model to predict the impact of currently used screening methods on ovarian cancer deaths.

These methods include testing for elevated levels of the protein CA-125 in the blood and pelvic imaging using ultrasound.

CA-125 levels rise in women with ovarian cancer, but they can also be elevated in women who are pregnant, who have other cancers, or non-cancerous conditions such as uterine fibroids.

The Duke researchers modified an established model of the progression of ovarian cancer to reflect the fast-growing and slower-growing forms of the disease.

They tested their model using early data from a large screening trial now under way in the U.K.

Instead of the 15% to 20% reduction in ovarian cancer deaths attributed to early screening based on the ‘one cancer’ model, the new model found that the death rate could be expected to fall by about 11% if annual screening using current strategies were routinely recommended for all postmenopausal women.

Havrilesky says this is because screening is more likely to pick up slow-growing cancers that are not as lethal.

The study appears online today in the online edition of the journal Cancer.

UK Trial Should Provide Some Answers

In the U.S., screening is generally reserved for women with a close family history of ovarian cancer or a genetic mutation that greatly increases their cancer risk.

Routine screening is not recommended for average-risk women.

Patricia Hartge, ScD, of the National Cancer Institute, tells WebMD that the Duke research adds to the evidence that more sensitive screening tests or strategies will be needed to significantly reduce deaths from ovarian cancer.

She says the U.K. study -- the largest ovarian cancer screening trial ever conducted -- should provide more answers when mortality data become available in 2014.

Instead of referring women for biopsy when CA-125 rises beyond a specific threshold, as researchers in a large U.S. trial did, investigators in the U.K. trial are watching to see how fast CA-125 levels rise.

“This approach involves fewer ultrasounds and fewer (exploratory) surgeries,” Hartge says. “We will know in a few years if it impacts survival.”

Havrilesky says she is cautiously optimistic that efforts to recognize ovarian cancer in its very early stages will help identify women who would benefit from prevention efforts such as surgical removal of the ovaries.

Until then, American Cancer Society Director of Cancer Screening Robert A. Smith, PhD says women should know the symptoms that might be early warning signs of ovarian cancer, including:

Abdominal, pelvic, and back pain

Bloating and swelling

Difficulty eating or feeling full quickly

Urinary symptoms

Of course, these symptoms are also commonly associated with other, far less serious conditions. But Smith says women with daily symptoms lasting more than a few weeks should see their doctor.